The present invention relates to pneumatic control of exit device hardware and more particularly to pneumatic control of a door latch through use of a pneumatic piston coupled to an air source through protected air lines.
Limiting uncontrolled entrance or exit from a building or other contained space is often required for safety and security. However, in an emergency situation it is necessary to have a procedure for quickly and safely exiting the building or contained space. Conventionally, such exit procedures involve use of doors having easy operating push bars or pads for panic exits.
Such doors are commonly found in buildings where security personnel are not available to control egress. To allow for centralized control of door lock operation, it is known to automatically operate the door latch from a remote location. For example, when a fire alarm is triggered by building smoke detectors, a signal can be sent to lock the latch mechanism of all fire doors, while still allowing mechanical override to allow for emergency exit of building occupants. Those individuals already within the building can escape, while entrance into fire threatened areas is limited. Alternatively, security personnel can remotely control unlocking of particular doors as necessary to allow ingress.
Such remote controlled doors are conventionally operated by electrical connections between each door and one or more control stations. In use, a control station operator flips a switch to either unlock or lock the latch bolt holding the door latch of the door in a closed position. In one class of latch devices, a solenoid assembly is used to hold the latch bolt in a retracted position. Activation of the control switch, whether automatically in response to a fire alarm or by the control station operator, breaks the electrical connection with the solenoid, and allows extension of the latch bolt. Optionally, a sensor can be placed to indicate whether the door latch is extended. This type of device has a failsafe operation, with any break in the electrical connection between the control station and the door causing deenergization of the solenoid and extension of the door latch.
However, electrical door control mechanisms may be too costly or unsafe to use in many situations. For example, currently available automatic electrical door control systems require installation of a costly separate power supply to operate electrical solenoid. In addition, safety regulations often do not permit electrical devices having a potential for sparking and electrical ignition in areas containing volatiles or other combustibles. To overcome these problems, pneumatically controlled door latch mechanisms for controlling ingress are needed.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.